Table of Contents Chapter Preview 4.1 Introduction to Atoms 4.2 Organizing the Elements 4.3 Metals 4.4 Nonmetals, Inert Gases, and Semimetals 4.5 Radioactive Elements • Chapter Preview • 4.1 Introduction to Atoms • 4.2 Organizing the Elements • 4.3 Metals • 4.4 Nonmetals, Inert Gases, and Semimetals • 4.5 Radioactive Elements

Chapter Preview Questions • 1. Groups of two or more atoms held together by chemical bonds are • a. elements. • b. molecules. • c. particles. • d. electrons.

Chapter Preview Questions • 2. When elements are chemically combined in a set ratio, they form • a. molecules. • b. matter. • c. elements. • d. compounds.

Chapter Preview Questions • 3. Which of the following is an example of an element? • a. copper • b. rust • c. concrete • d. water

Chapter Preview Questions • 4. Two compounds with different properties are • a. C and O. • b. H and O. • c. CO and CO2. • d. Cl and Ar.

Imagine you have a piece of • aluminum foil, and you cut it • in half. If each of these pieces is • cut in half a second, third, and • fourth time, the pieces become • smaller but are still aluminum. • How small must a piece be so • that at the next cut it will no • longer be aluminum? How is the periodic table organized?

Greek Word Origins First letter of the Greek alphabet Alpha particle alpha

Greek Word Origins atomos Atom, atomic number, atomic mass Cannot be cut; indivisible

Greek Word Origins beta Second letter of the Greek alphabet Beta particle

Greek Word Origins di Two, double Diatomic molecule

Greek Word Origins Third letter of the Greek alphabet gamma Gamma radiation

Greek Word Origins hals Salt, relating to salt Halogen

Apply It! Review the Greek origins and meanings in the chart. What is the meaning of the prefix di- in diatomic? Predict the meaning of diatomic molecule. Revise your definition as needed. Sample: Since diatomos means “two atoms,” di- probably means “two.”

End of Chapter Preview

Section 1:Introduction to Atoms • How did atomic theory develop and change? • What is the modern model of the atom?

Atomic Theory and Models • Dalton thought that atoms were like smooth, hard balls that could not be broken into smaller pieces.

Atomic Theory and Models • Thomson suggested that atoms had negatively charged electrons embedded in a positive sphere.

Rutherford’s Gold Foil Experiment • Rutherford was surprised that a few particles were deflected strongly. This led him to propose an atomic model with a positively charged nucleus.

Later Atomic Models • Through the first part of the twentieth century, atomic models continued to change.

Modern Model of an Atom • This model of a carbon atom consists of positively charged protons and neutral neutrons in a nucleus that is surrounded by a cloud of negatively charged electrons.

Particles in an Atom • An atom is composed of positively charged protons, neutral neutrons, and negatively charged electrons. Protons and neutrons are about equal in mass. An electron has about 1/2,000 the mass of a proton or neutron.

Isotopes • Atoms of all isotopes of carbon contain six protons and six electrons, but they differ in their number of neutrons. Carbon-12 is the most common isotope.

More on Atomic Structure • Click the PHSchool.com button for an activityabout atomic structure.

End of Section:Introduction to Atoms

Section 2:Organizing the Elements • How did Mendeleev discover the pattern that led to the periodic table? • How are the elements organized in the modern periodictable?

The Periodic Table • Elements are organized into rows and columns based on their atomic number.

Periodic Table Activity • Click the Active Art button to open a browser window and access Active Art about the periodic table.

Finding Data on Elements • Each square in the periodic table lists four pieces of information: an element’s atomic number, chemical symbol, name, and atomic mass.

End of Section:Organizing the Elements

Section 3:Metals • What are the physical properties of metals? • How does the reactivity of metals change across the periodic table? • How are synthetic elements produced?

Metals in the Periodic Table • The metals in Group 1, from lithium to francium, are called the alkali metals. Alkali metals react with atoms of other elements by losing one electron.

Metals in the Periodic Table • Group 2 of the periodic table contains the alkaline earth metals. These elements are not as reactive as the metals in Group 1, but they are more reactive than most other metals.

Melting Points in a Group of Elements • The properties of elements within a single group in the periodic table often vary in a certain pattern. The following graph shows the melting points of Group 1 elements (alkali metals) from lithium to francium.

Melting points decrease from lithium to francium. Reading Graphs: As you look at Group 1 from lithium to francium, describe how the melting points of the alkali metals change. Melting Points in a Group of Elements

New element 119 should have a melting point of approximately 25ºC or lower. Predicting: If element number 119 were synthesized, it would fall below francium in Group 1 of the periodic table. Predict the approximate melting point of new element 119. Melting Points in a Group of Elements

Cesium, francium Interpreting Data: Which of the alkali metals are liquids at 35ºC? Melting Points in a Group of Elements

Metals in the Periodic Table • The transition metals are less reactive than the metals in Groups 1 and 2.

Metals in the Periodic Table • Only some of the elements in Groups 13 through 15 of the periodic table are metals.

Metals in the Periodic Table • Lanthanides are usually found together in nature, always combined with other elements.

Metals in the Periodic Table • The elements below the lanthanides are called actinides. Many of these elements are so unstable that they last for only a fraction of a second after they are made.

Links on Metals • Click the SciLinks button for links on metals.

End of Section:Metals

Section 4:Nonmetals, Inert Gases, and Semimetals • What are the properties of nonmetals and inert gases? • How are semimetals useful?

Properties of Nonmetals • When nonmetals and metals react, electrons move from the metal atoms to the nonmetal atoms.

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